Dynamo-electric machine.



No. 732,906. PATENTED JULY 7, 1903.

C. P. STEINMETZ. DYNAMC ELECTRIC MACHINE.

APPLICATION FILED APR. 9, 1900 H0 KODEL. 2 SHEETS-SHEET 1.

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PATENTED JULY 7, 1903'.

G. P. STEINMETZ.

APPLIOATIOI nun an. a, mo.

CharlesPSteinFnetq Fig. 4.

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Witnesses:

f a I UNIT-ED STATES rammed an 7, 1903.

PATENT OFFICE.

CHARLES P. STEINMETZ, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERALELECTRIC COMPANY, A CORPORATION OF NEW YORK.

DYNAMO-ELECTRIC MACHINE.

SPECIFICATION forming part of Letters Patent N 0. 732,906, dated July 7,1903.

Application filed April 9, 1900. Serial No- 12,l59. (N0 model.-

To all whom it may concern:

Be it known that I, CHARLES P. STEINMETZ, a citizen of the UnitedStates, residing at Schenectady, county of Schenectady, State of NewYork, have invented certain new and useful Improvements in DynamoElectric Machines, of which the following is a specification.

Generally speaking, my present invention relates to certain improvementsin dynamoelectric machines whereby the heating of the conductors isreduced, certain other losses partially eliminated, and the output ofthe machine as a whole increased.

The invention is particularly useful in connection with rotaryconverters and is equally valuable whether the converter be used forchanging alternating current into direct current or the reverse. It isto be understood, however, that although the invention is especiallydesirable in connection with rotary. converters it is not to beconsidered as limited thereto, but rather as embodying such applicationsof the same as are included within the terms of the claims appendedhereto.

Briefly characterized, myinvention includes the idea of adynamo-electric machine having connected thereto a plurality of sets ofleads which in normal operation carry currents of substantially the samephase.

A more complete understanding of the organization and mode ofoperation'of my invention, together with the advantages accompanying theuse of the same, will be had by reference to the following description,taken in connection with the accompanying drawings, in which- Figure 1shows the application of the invention to a single-phase alternating-current system, Fig. 2 being a diagram explanatory of the same. Fig. 3shows the invention as embodied in a multiphase system of distribution,Fig. 4: being a similar explanatory diagram.

The application of the invention as illustrated in Figs. 1 and 2 of thedrawings comprises a system in which single-phase alternating current issupplied to a rotary con vertcr, by which it is changed into directcurrent. Single-phase supply-mains are shown at 1 2, and from thesemains branches are tapped off leading to the primary winding 3 of atransformer the secondary of which is divided into two sections,(numbered 4 and 5, respectively.) Leads extend from the secondaries 4 5and are connected to the armature-winding of a rotary converter, (shownin the drawings diagrammatically at 7.) In the arrangement shown, thearmature-winding '7 is provided with four taps 8, 9, 10, and 11, leadingto adjacent collector-rings. It is not essential in order to obtain thebeneficial effects of my invention that these taps should be connectedto the armature-winding of the converter in a precise manner, sinceconsiderable latitude is permissible in making these connections, aswill presently be seen.

In the arrangement shown in Fig. l the taps 8 10 are connected to thearmature-Winding 7 at points displaced from each other by onethird ofthe polar pitch, which in bipolar machines represents an arc of onehundred and twenty degrees. The corresponding taps 9 and 11 are likewiseconnected to the armature-winding 7 at points displaced from each otherby the same are. It is to be noted that the chords of these two arcs arearranged so as to lie parallel to the same diameter, (represented by thedotted line 12 in Fig. 2,) by reason of which arrangement the inducedelectromotive force between one set of taps will be in the same phase asthat between the other set of taps. This relation of electromotiveforces is shown diagrammatically in Fig. 2, in which the dottedinscribing-circle 120 denotes the locus of electromotive forces aboutthe various points in the armaturewinding 7, while the parallel lines 13and 14 forces generated between or impressed upon the two sets of taps 810 and 9 11, respectively.

The taps 8 10 are connected to leads 15 16, extending from the secondary4, while the taps 9 11 are similarly connected to leads 17 18, extendingfrom the secondary 5. The secondaries 4 and 5, being inductively relatedto the same primary, therefore generate currents of the same phase,which, being led to respective sets of collector-rings, are then fedinto the armature-winding 7, creating therein magnetomotive forces whichcooperate to the extent that they are in the same phase with each other,but which at the same time are to a certain extent distinct in that theyare produced by currents fed into the armature-winding through separatecircuits. A resultant magnetization is, however, given to the armaturesimilar to that which would exist if a single-phase current were fedinto the armature at points diametrically opposite from each other, withthe distinction,however, that in the two cases the distribution ofcurrents in the armature-winding is different.

The rotary converter is provided with a commutator 19 of ordinary form,suitably connected in the ordinary manner to points in thearmature-winding 7. To prevent confusion in the drawings, theseconnections between the commutator-segments and the armature-windinghave been omitted; but the construction, being so common, will bereadily understood without the aid of illustration. Direct-current mains20 and 21 are connected to commutator-brushes 22 and 23, bearing on thecommutator 19, and supply current to translating devices of anyappropriate charactersuch, for example, as lamps L.

A feature somewhat incidental to the invention thus described may beemployed in connection therewith for the purpose of obtainin g a neutralconductor to be used in connection with the direct-current mains 20 and21 to form therewith a three-wire direct-current system. To secure sucha neutral conductor, an inductance-coil of appropriate ca pacity isconnected between the middle points, respectively, of the secondarywindings l and 5. This corresponds to connecting the middle points inthe lines 13 14, representing the electromotive forces of thesecondaries 4E and 5. The straight horizontal dotted line in Fig. 2illustrates the connection between the middle points of theelectromotive-force lines 13 and 14, and it will be noted that this linepasses through the center of the inscribing-circle The center of thedotted line being then the center of the inscribing-circle, whichrepresents the electromotive forces existing throughout thearmature-winding '7, therefore corresponds to a point of neutralpotential with respect to these electromotive forces. It a conductor beled from the middle point in the length of the inductance-coil 24;,connected to the middle points of the secondaries 4 and 5, it will havea potential which is neutral with respect to the eleetromotive forcesacting about the armature-winding 7, and therefore neutral with respectto the electromotive force impressed on the direct-current mains 20 and21, which derive current from said winding. Such a neutral conductor isshown at 25 and extends from the middle point in the length of theinductance-coil 24c and cooperates with the direct-current mains 20 and21 to produce a three-wire direct-current system.

To render clear the mode of operation of the apparatus as a whole, letit be supposed that the rotary converter be supplied with alternatingcurrent through the leads or supply-mains 15 to 18, inclusive, and thatfor convenience the current is in phase with the electromotive force.The field structure being excited in the usual manner by means of directcurrent derived from the mains 20 and 21 or otherwise a synchronousrotation of the converter-armature takes place, while the alternatingcurrents flowing into the armature through both circuits between the twosets of taps 8 10 and 9 11, respectively, beingin phase with each otherwill simultaneously change in value, reaching a maximum when the polarlines of the circuits mentioned lie across the field at right angles tothe direction of the poles and passing through intermediate values asthe armature progressively shifts in position. Since the direct currentflowing out of the converter is constant throughout a revolution whilethe alternating current passes through a complete cycle, it follows thatthe resultant current in each armatureconductor lying within. either ofthe circuits between the respective sets of taps 8 10 and 9 11 varies asthe conductor changes from position to position, the range of variation,as in the ordinary rotary converter, being least in conductors situatedmidway between the taps and greatest at and near the points ofconnection of these taps. As to the armatureconductors lying betweentaps of the same polarity-as, for-instance, between. the taps 8 9theconditions are different. The alternating electromotive forces impressedon the two sets of taps, respectively, being of the same value and inthe same phase, are therefore equal to each other at every instant, fromwhich it follows that no difference of potential due thereto existsbetween taps of corresponding polarity, so that no current directly dueto the alternating electromotive forces will flow in thearmature-00nductors between these taps. The only current flowing inthese conductors will therefore be the direct current which traversesthe directcurrent mains of the machine, and since this current isdivided in passing through the armature the current which flows in theconductors mentioned is uniform and equal in value to one-half of thatflowing through the commutator-brushes connected to the directcurrentmains. Referring to the drawings, it will be seen that the current inthe armature-conductors between the taps 8 9 an d also between the taps1O 11 will be uniform and equal to one-half that in the direct-currentmains. Vith multipolar machines the value of current is of coursecorrespondingly changed, as will be obvious.

In conductors midway between taps of opposite polarity the Wave ofalternating current is opposed in phase to the rectangular wave ofdirect current, so that when the alternating wave is at its Zero-pointthe full direct current flows. \Vhen the two currents become equal toeach other, the resultant is zero, while at maximum alternating currentthe resultant is the excess of alternating over direct. This excess inthe ordinary singlecircuit rotary converter is equal in value to thedirect current and in the double-circuit converter,herein disclosed,somewhat greater than the direct current, since in the latter machinethe alternating electromotive force is less and the alternating currenttherefore greater than in the former.

In conductors at or near the taps for the alternating leads theconditions are different, since the maximum current flows in theseconductors when the taps are nearer to the commutator-brushes. In suchcoils the rectangular wave of direct current is displaced from thealternating wave, the displacement being such that in the ordinarysingle-circuit converter the maximuni alternating current occurs at theinstant the direct current reverses, while in the double-circuitconverter it occurs when the commutator-brushes are in connection withpoints between taps of the same polarity-for example, taps 8 9-andtherefore at points in the alternating wave displaced from the maximumby an angle represented by a portion of the angle between theconnections of the taps. As analternating-current tap passes under acommutatorbrush the direct current reverses,so that when the tap is onone side of the brush the alternating and direct currents in a conductorconnected to the tap are added, while on the other side they aresubtracted. The result is that the maximum current in conductors at ornear the taps is the greater the less the phase displacement between thetime of maximum alternating current and the instant of reversal of thedirect current.

In the single-circuit converter the direct current reverses as the tapspass under the comm utator-brushes, and therefore at a time when thealternating current is a maximum, while in the double-circuit converterthe taps pass under the commutator-brushes and the reversal takes placeat a time when the alternating current is considerably below its maximumvalue.

In the double-circuit converter the maximum resultant current inconductors at and near the taps is so much smaller compared with thesingle-circuit converter that it more than compensates for the increasedheating of conductors in the region midway between the leads. Thedouble-circuit converter therefore possesses the valuable advantage ofincreased capacity due to decreased heating and-at the same time of areduction in the excessive heating in and near the taps characteristicof rotary converters, and particularly those of the sin gle-phase typeThe angular displacement of the taps is somewhat a matter of compromise,and within limits the heating in conductors situated between but nearestto taps of opposite polarity isreduced as the are between thetaps isdecreased, while the heating of conductors farthest from the taps isincreased. Provided the arc is not too great, the result of feedingcurrents of the same phase into or out of the armature-winding at pointsseparated from each other results in rendering heating of the conductorsconsiderably less unequal than is the case in the ordinary single-phaserotary converter now in use and at the same time reduces the meanheating, and so increases the capacity of the machine. With an arc ofseparation of the taps into the armature-winding of one-sixth of thepolar pitch, as represented in Fig. 1 of the drawings, the heating ofthe conductors at these taps is approximately one-third less than theheating in the ordinary single-phase rotary converter, while the meanheating of all the conductors, taken together, is approximately fifteenper cent. less, the percentages in reduction of heating given being madeup for by increase in heating in conductors situated between the taps ofthe armature-winding. As stated, however, the mean heating is reduced,because the decrease of heating at the taps preponderates over theincrease in heating between the taps.

In addition to the decrease in armatureheating and the consequentincrease in capacity of the machine there are certain other advantageswhich flow from the use of my invention.

In the ordinary single-circuit single-phase rotary converter thedirect-current armature reaction does not vary except as the currentvaries, while that due to the energy component of the alternatingcurrent varies be tween zero and a maximum equal to twice that of thedirect current. Since the armature reactions due, respectively, to thedirect current and alternating current are in opposition to each other,the result is an oscillating reaction varying between a maximum in onedirection equal in value to the direct-current reaction and an equalvalue in the opposite direction. The sweeping of lines of force back andforth through the pole-faces of the fieldmagnets due to this oscillatingreaction gives rise to eddy-currents and similar losses and seriouslyinterferes with proper commutation. By the use of my invention thisoscillating reaction is considerably reduced, since the maximumresultant ampere-turns of the alternating current is decreased. Thecommutation is thus improved and losses due to eddy-currents,hysteresis, &c., decreased.

My invention is not limited to use in 0011- nection with single-phasemachines, but is applicable to multiphase machines as Well,

the difference between Fig. 3 of the drawings for purposes ofillustration showing the invention as applied to a two-phase rotaryconverter. The two-phase current is supplied over mains 28 to 31,inelusive, to two primaries 32 and 33. of these primaries is providedwith two secondary windings, (indicated, respectively, at 34 35 and so37.) V

The converter-armature is indicated at 38, and if a bipolar machine,such as indicated in the drawings, is tapped at eight points,

Each

separated from each other by equal angles in the instance shown. The twosecondaries 34 and 35 are connected to the taps 39 40 and 41 42 insubstantially the same manner as in Fig. 1, the two secondariessubtending arcs corresponding to the chords 43 44 in the explanatorydiagram Fig. 4. The secondaries 36 and 37 are similarly connected totaps 45 46 and 47 48, the points of connection corresponding to parallelchords 49 50 at right angles to the parallel chords 43 44, as shown inFig. 4. The rotary-converter armature is provided in the ordinary mannerwith a commutator 51, upon which bear brushes connected todirect-current mains 52 53, leading to a direct-current distributionsystem. (Not shown.) In Fig. 3 pole-pieces corresponding to a bipolarconstruction are shown; but it will be understood that both in thisfigure and in Fig. 1 the number of poles is unimportant so far as theinvention is concerned, and the machine may be either bipolar ormultipolar.

The arrangement shown in Fig. 3 is similar in its action to that in Fig.l, in that the heating in the conductors adjacent to the taps 0r leadsof the armature is less, and the mean heating of the conductors as aWhole is less than in the ordinary construction of two-phase rotaryconverters in which current of a given phase is fed into the armature attwo points only for each pair of poles. Since in a multiphase rotaryconverter the armature reaction of the alternating current balances thatof the direct current, there is in this case of course no change in thatrespect. There is, however, the advantage that the local variations ofmagnetomotive force about thearmature are considerably reduced, thusreducing losses due to eddy-currents, hysteresis, &c.

It is of course to be understood that the applications of my inventionto rotary converters above described are valuable irrespective ofwhether alternating current is changed to direct or the reverse, so thatmy claims are not to be construed as necessarily limited to use in oneof these relations only. Moreover, although I have illustrated myinvention in connection with a single phase rotary converter and atwo-phase rotary converter it is of course to be understood that it isin no sense limited to use in the particular relations shown, but ismuch more extended in its ap plication, and I therefore wish my claimsto the invention to be considered accordingly.

WVhat I claim as new, and desire to secure by Letters Patent of theUnited States, is-

1. A rotary converter having a plurality of separate alternating-currentleads of like polarity connected to different points in thearmature-winding of said rotary converter.

2. A single-phase rotary converter having a plurality ofalternating-current leads transmitting currents of the same phase andconnected to different points in the armaturewinding of said rotaryconverter.

3. A rotary converter having a plurality of separate alternating-currentcircuits of the same phase, each circuit connected to points in thewinding of said rotary converter different from the points of connectionof the other circuit or circuits.

4. A single-phase rotary converter having a single armature-winding, acommutator for conveying direct current to or from said winding, andalternating-current leads connected to said winding so that theelectromotive force of the direct current is higher than the maximumelectromotive force of the alternating current.

5. A rotary converter having an armaturewinding, a commutator connectedto said winding, and alternating-current leads connected to said windingin such relation that the electromotive force of the direct current ishigher than the maximum electromotive force of the alternating current.

6. A dynamo electric machine provided with an armature and a commutatortherefor, direct-current leads extending from the commutator, and pairsof alternatingcurrent leads connected to fixed points in thearmature-winding so as to convey alternating currents of the same phase,the points of connection of leads of the same polarity being adj acentto each other whereby armature-conductors lying between said adjacentpoints of connection carry only direct current while otherarmature-conductors carry a combination of alternating and directcurrent.

7. A dynamo-electric machine having a winding, and sets of cooperatingterminals connected to certain fixed points of said windingcorresponding to the ends of parallel chords.

8. A rotary converter having a winding,and sets of cooperating terminalsconnected to certain fixed points of said winding corresponding to theends of parallel chords.

9. A single-phase rotary converter having a winding, and sets ofcooperating terminals connected to certain fixed points of said windingcorresponding to the ends of parallel chords.

10. A dynamo-electric machine having a winding, terminals in fixedelectrical connection to points in said winding corresponding to theends of parallel chords, and a plurality of leads connected to saidterminals and carrying currents of the same phase.

11. A single-phase, alternatingcurrent dynamo-electric machine having awinding, and circuits connected to fixed points in the Winding having adifference of potential less than the maximum existing in said winding.

12. The combination of a dynamo-electric machine and a plurality ofseparate sets of leads carrying currents of the same phase and in fixedelectrical connection with a winding of said machine, the points ofconnection of one set of leads being separate from the points ofconnection of another of said sets of leads.

13. The combination of a dynamo-electric machine, a plurality of sets ofleads carrying currents of the same phase, connections between one setof leads and certain points in a winding on said machine, and separateconnections between another set of leads'and a different set of pointsin said winding.

14. Thecombination of a plurality of transformer-windings carryingcurrents of the same phase, a dynamo-electric machine provided with awinding, connections from fixed points in said Winding to one of saidtransformer-windings, and separate connections from other fixed pointsin said winding to another of said transformer-windings.

15. The combination of a plurality of separate sources of alternatingcurrent of the same phase, a dynamo-electric machine provided with awinding, fixed electrical connections from certain points in saidwinding to one of said sources, and separate fixed electricalconnections from other points in said winding to another of saidsources.

16. The combination of a dynamo-electric machine, separate sources ofcurrent of the same phase, and connections to certain fixed points ofthe armature-winding of the machine for feeding said currents thereto.

17. The combination of aplurality of transformer-windings carryingcurrents of the same phase, a dynamo-electric machine provided with anarmature-winding, connections from fixed points in said armature-Windingto one of said transformer-windings, and other fixed connections fromother points in said armature-Winding to another of saidtransformer-windings.

18. The combination of a plurality of sources of alternating current ofthe same phase, a dynamo-electric machine provided with a Winding,connections from fixed points in said Winding to one of saidsecondaries, and other connections from certain other fixed points insaid winding to another of said secondaries. Y

20. A rotary converter having a plurality of separatealternating-current circuits of the same phase, direct current mainsleading from the direct-current terminals of the machine, and a neutralconductor connected with a point of neutral potential on thealternating-current system and cooperating with said direct-currentmains.

21. An a1ternating-current dynamo-electric machine connected through aplurality of separate circuits of the same phase to an alternating-current system, a direct-current sys tem also connected to saiddynamo-electric machine,and a conductor connected to a point of neutralpotential on said alternating-clu rent system and cooperating With thecon= ductors of the direct-current system,

In witness whereof I have hereunto set my hand this 7th day of April,1900.

CHARLES P. STEINMETZ.

Witnesses:

BENJAMIN B. HULL, MABEL E. JAcoBsoN.

